IN-VITRO DETERMINATION OF DIRECT ANTIMICROBIAL EFFECT OF CALCIUM HYDROXIDE

The objective of this study was to determine in vitro the time require d for calcium hydroxide in direct contact with microorganisms to expre ss its antimicrobial effect. The microorganisms used were: Micrococcus luteus (ATCC-9341), Staphylococcus aureus (ATCC-6538), Fusobacterium nucleatum (ATCC-25586), Pseudomonas aeruginosa (ATCC-27853), Escherich ia coli, and Streptococcus sp. The strains were cultivated in Brain He art Infusion (BHI), with the exception of F. nucleatum (BHI-PRAS). Pur e and mixed suspensions of the microorganisms were prepared. Paper con es immersed in these substances were covered with calcium hydroxide pa ste, and after 0, 1, 2, 6, 12, 24, 48, and 72 h and 7 days they were t ransferred to an appropriate medium to observe the growth and multipli cation of the microorganisms. Incubation was conducted at 37 degrees C for 48 h, according to the requirements of oxygen of each microorgani sm. The antimicrobial effect of calcium hydroxide was shown to occur a fter 12 h on M. luteus and F. nucleatum, 24 h on Streptococcus sp, 48 h on E. coli, and 72 h on S. aureus and P. aeruginosa. Mixture II (M. luteus + Streptococcus sp + S. aureus) was sensitive to calcium hydrox ide antimicrobial potential after 48 h, whereas mixture I (M. luteus E. coli + P. aeruginosa), mixture III (E. coli + P. aeruginosa), and mixture IV (S. aureus + P. aeruginosa) were inactivated after 72 h of exposure.